Allergic contact dermatitis from sodium pyrithione in metalworking fluid

Delayed diagnosis of occupational contact dermatitis from sodium pyrithione in a metalworking fluid

“…being a more practical diluent than aq. (1), but our patient did not react to zinc pyrithione on patch testing, even though he was tested with a higher concentration than he was with sodium pyrithione (sodium pyrithione 0.1% = 0.007 mol; zinc pyrithione 1.0% = 0.032 mol). This discrepancy may be due to different absorption from the 2 vehicles.…”

“…The patient was allergic to sodium pyrithione (0.1% aq., Chemotechnique Diagnostics, Malmö, Sweden), tested twice to confirm the diagnosis. Sodium pyrithione is purchased by Chemotechnique Diagnostics as a 40% solution in water, termed sodium omadine, but the patch test concentration is 0.1% active ingredient (personal communication, Chemotechnique Diagnostics, Malmö, Sweden) (1). Sodium pyrithione was a component of his MWF, present at 0.1–1.0%.…”

“…We also patch tested several MWFs but not the one that this patient worked with (2). Sodium pyrithione has been present in MWF series since at least the 80 s, but only 2 cases of contact allergy to this preservative in MWFs have been published (1, 3).…”

“…Zinc pyrithione, another metal salt of pyrithione, used in antidandruff shampoos, is said to cross‐react with sodium pyrithione, since the hapten is the pyrithione moiety (1). The patient denied using such shampoos and had also never experienced any skin complaints from shampoos.…”

“…In the 2 previous reports (1, 3), zinc pyrithione was not tested. Since 1995, we have had 2 patients reacting to sodium pyrithione but they did not work with MWFs, the clinical relevance was unclear and they were not tested with zinc pyrithione.…”